POS0653 CAN DOSAGE OF INFLIXIMAB BE ADJUSTED TO 8 WEEK INTERVALS WITHOUT LOSING EFFICACY IN ARTHRITIS PATIENTS ON MAINTENANCE THERAPY WITH MORE FREQUENT INFUSIONS?
Authors: E. Lindqvist, B. Månsson
Journal: Annals of the Rheumatic Diseases (2022)

Background Infliximab is usually given every 8 weeks. To increase dosage, the dose can be increased or the interval between infusions shortened. To minimize patient visits and workload for the medical staff during the Corona pandemic, we intended to change all infliximab infusions to 8 week intervals. For patients with inflammatory bowel disease, a trough level of serum (s-) concentration of infliximab of 3-7 µg/ml is recommended. In Rheumatology the usefulness of assessing s-concentration is controversial. (1, 2) Objectives To evaluate if 8 week interval infliximab dosage, with retained weekly dose, can be used in arthritis patients, without worsening of disease activity or general health and study if s- concentration of infliximab is related to disease activity and general health. Methods All arthritis patients on stable infliximab treatment were evaluated at the time for infliximab infusion. Disease activity, DAS28-CRP, VAS pain, global, fatigue, doctors’ global, HAQ, and ASDAS-CRP, BASFI for spondyloarthritis (SpA) patients were registered in the Swedish Rheumatology Quality registry (SRQ). Blood tests for CRP, ESR and s-concentration of infliximab were taken before infusion start. S-concentration was analysed at Karolinska Hospital, Solna, Sweden with an in-house ELISA. Antibodies were assessed if s-concentration was &lt;0.5 µg/ml. Patients with infusion intervals less than 8 weeks were recommended a switch to 8 week intervals with maintained weekly dose of infliximab. The new dose was given the same day and patients with changed doses were re-evaluated after 24 weeks. Paired samples T-test and Wilcoxon signed rank test for paired data were used for comparison of disease activity and general health after dosage change. Linear regression analyses were used to explore associations between s-concentration, disease activity and general health. Results Of 91 assessed patients, 66 with shorter intervals were recommended dosage change. The remaining 25 patients had infliximab every 8 weeks and served as controls. For baseline characteristics see Table 1. Dosage was changed in 58 patients and 90% (n=52) remained on 8 week intervals after 24 weeks, with a mean (SD) dose of infliximab of 5.3 (1.9) mg/kg. All assessed disease variables (DAS28-CRP, VAS pain, global, fatigue, Dr global, HAQ, ASDAS-CRP, BASFI, CRP and ESR) remained unchanged (p=0.051 (pain) – 0.83) (Figure 1 A, B) while S-concentration was lower (p&lt;0.001) at follow up. S-concentration of infliximab did not relate to disease activity neither at baseline nor at follow up (p=0.15-0.24). (Figure 1 C, D) Table 1. Patient characteristics at inclusion Interval 4-7 w, n=66 8 w, n=25 Age, years 56 (15) 58 (14) Female sex 42 (64%) 11 (44%) Disease duration, years 20 (12) 20 (10) Clinical diagnosis: RA/JIA+arthritis UNS 14 (21%)/ 5 (8%) 7 (28%)/2 (8%) SpA/PsA 31 (47%)/16(24%) 10 (40%)/6 (24%) S-concentration infliximab µg/ml 9.0 (4.6-14.0) 3.4 (1.1-5.1) Antibodies against infliximab 2 (3%) 3 (12%) ESR 24 (16-37) 24 (15-42) CRP 1.3 (0.8-2.3) 1.1 (0.6-2.9) DAS28-CRP 2.8 (1.1) 2.6 (1.2) HAQ 1.0 (0.38-1.38) 0.38 (0.25-0.85) Patients’ VAS pain 23 (8-50) 20 (3-32) Patient’s VAS global health 31 (11-49) 15 (2-48) Doctors’ VAS global health 9 (6-11) 7 (2-12) ASDAS-CRP 1.8 (0.7-2.5) 1.2 (0.6-1.5) BASFI 3.3 (1.3-6.1) 1.4 (0.3-2.4) Concomitant csDMARD 39 (59%) 16 (64%) Glucocorticoids 12 (18%) 1 (4%) Mean (SD), median (interquartile range (IQR)) or n (%). ASDAS-CRP and BASFI; 41 SpA patients. Conclusion Adjustment of infliximab dosage to every 8 weeks worked for a majority of the arthritis patients in this clinical setting without worsening of disease activity or general health. S-concentration of infliximab did not relate to disease activity or general health. References [1]Syversen SW et al. JAMA. 2021 Dec 21;326(23):2375-2384. [2]Mehta P et al. Front Immunol. 2020 Apr 7;11:589. Disclosure of Interests None declared